This invention relates in general to fluid conduits and containers, and more particularly to fluid-containing structures which are compact and light in weight and to a process for making the same.
The fuel lines and tanks of military aircraft are extremely vulnerable to antiaircraft projectiles, and of course, the rupture of a fuel line or fuel tank can have disasterous affects, since it will deprive the aircraft engines of their fuel supply and can result in the spillage of flammable fuel into areas where it might easily be ignited. To reduce these hazards, the typical metal fuel line tube for military aircraft is encased in natural gum rubber which is in turn encased in a fabric overwrap to maintain it in place. A projectile penetrating the metal tube will also penetrate the gum rubber, but the fuel which leaves through the holes in the metal tube will cause the gum rubber to swell and seal the rupture. The metal tube, however, tends to flare outwardly at the exit hole and the flared segments of metal surrounding the hole hold some of the gum rubber sealant away from the hole. The flared segments left by the exiting projectile are often referred to as "petals", and the sealant layer must be made thick enough to accommodate the petalling. This increases the weight and bulk of the fuel line substantially.
To reduce the weight of such fuel lines it has been proposed that a light weight foam layer be interposed between the metal tube and the sealant layer so that the light weight foam will accommodate the petalling, while the surrounding sealant material performs only the sealing function. Use of a so-called foam standoff, however, does not reduce the bulk of the fuel line, and indeed often increases the diameter to such an extent that the fuel line cannot be used as a replacement for existing lines without enlarging bulkhead apertures, bracketing, and the like.
It has also been suggested that actual fuel confining tube be formed from various plastic materials having a high modulus of elasticity so that that material will not petal, but instead will fracture to leave a clean hole therein when penetrated by a projectile. However, to obtain sufficient strength these materials must have relatively thick walls. Moreover, they are often incompatible with fuels. Also, they do not conduct electricity and as a result electric charges built up by the moving fuel are not dissipated to ground. This is the so-called triboelectric phenomenon.
Non-metal fuel tubes, as well as other types of non-metal conduits, possess another significant disadvantage, and that is that they cannot be coupled easily and securely.